Gray Layers and the Erosion of Chromium Plated Gun Bore Surfaces

Download or read book Gray Layers and the Erosion of Chromium Plated Gun Bore Surfaces written by and published by . This book was released on 1999 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present report describes observations and analyses in a survey study of erosion damage in chromium plated gun bore surfaces. Sections of three fired chromium plated 120-mm M256 gun tubes and two 155-mm gun tubes (M199 and XM297) were examined by optical microscopy, laser scanning confocal microscopy (LSCM), and electron microprobe analyses. These tubes experienced significant erosion damage and chromium loss. A rifled portion of the 155-mm M199 tube was plated with low contractile (LC) chromium and the 155-mm XM297 and 120-mm M256 tubes were plated with high contractile (HC) chromium. New insights regarding the erosion process and the origin of chromium loss are obtained by investigation of the initial damage to the steel at the tips of the fine cracks in the chromium. Reaction products from gas-metal interactions at the gun bore surface are normally difficult to find because of gas wash effects. Examination of unetched specimens from a variety of fired tubes shows that these products remain in lace in the relatively protected regions beneath the chromium when chromium crack widths are small. The initial damage is manifested as gray layers or gray regions in the steel at the tips of the fine chromium cracks. Electron microprobe analyses indicate that these gray layers are composed of iron sulfide, iron oxide, or mixtures of the two compounds.